The present invention relates to a fingerprint input apparatus, for example, used in a system that verifies an identity of an individual in a security system.
Conventional fingerprint input apparatuses which detect fingerprints as an optical image are disclosed in Japanese Patent Publication SHO 55-13446 and Japanese Patent Publication SHO 58-144280.
In one conventional fingerprint input apparatus, a finger is placed on a plane surface of an optically transparent material. A light source is positioned such that the light emitted therefrom is incident on the plane surface at an angle greater than the critical angle. Some of the incident light will be scattered while that corresponding to the fingerprint will be reflected. An image sensor is positioned to receive the reflected light, thereby detecting the fingerprint pattern. However, the positioning of the image sensor must be done carefully if the reflected light is to be received properly. Further, interference from the scattered light reduces the contrast of the light received at the image sensor, and reduces the quality of the fingerprint pattern detected.
In another conventional fingerprint input apparatus, a similar construction to that described above is employed. However, the image sensor is positioned so as not to receive any of the light reflected by the fingerprint. Thus, only the scattered light is detected, and the fingerprint pattern is detected as a result of an absence of light. However, the amount of light incident on the image sensor is low, and therefore the contrast is also low. Further, the positioning of the image sensor and the light source must be done carefully if direct interference from the light source on the image sensor is to be avoided.